The present invention generally relates to valve deactivation and two-step variable valve lift systems in internal combustion engines. More particularly, the present invention relates to a roller finger follower rocker arm device that accomplishes valve deactivation and/or cam profile mode switching in internal combustion engines.
Deactivation roller finger followers (RFFs) typically include a body and a roller disposed on a hollow shaft. A locking pin assembly of the deactivation RFF is disposed within and carried by the hollow shaft. The locking pin assembly is switched between a coupled and a decoupled state. In the coupled state the locking pin couples the shaft to the body, whereas in the decoupled state the locking pin assembly decouples the shaft from the body. The roller is engaged by a cam of an engine camshaft. With the locking pin assembly in the coupled state/position, rotation of the cam is transferred through the roller, shaft and locking pin to pivotal movement of the RFF body. The pivoting RFF body actuates an associated engine valve. With the locking pin assembly in the decoupled state/position, rotation of the cam is not transferred to pivotal movement of the RFF body. Thus, the associated engine valve is not actuated. Rather, the shaft is reciprocated within grooves formed in the RFF body. The grooves retain and guide the reciprocation of the shaft.
A two-step RFF operates in a manner similar to a deactivation RFF. One particular difference between the operation of a deactivation RFF and a two-step RFF occurs in the decoupled mode of operation. The body of a deactivation RFF is typically engaged by zero-lift cam lobes, which maintain the deactivation RFF body in a static position. The zero-lift cam lobes do not pivot the RFF body and thus the associated engine valve is not actuated. In contrast, low lift, rather than zero lift, cam lobes engage the two-step RFF body or roller bearings affixed thereto. In the decoupled mode, the low-lift cam lobes pivot the two-step RFF body a relatively slight amount. The pivoting of the body of the two-step RFF in the decoupled mode, in turn, reciprocates the associated engine valve according to the lift profile of the low-lift cam lobe. In the coupled mode, a two-step RFF operates in a substantially similar manner to a deactivation RFF, i.e., the cam engages the roller thereby pivoting the RFF body and actuating the associated valve.
The roller and shaft of these switching RFFs (i.e., deactivation and two-step RFFs) are typically disposed within a cavity of the RFF body. The shaft and roller undergo a degree of undesirable movement or play in a direction that is generally transverse to the RFF body during their reciprocation within the grooves of the RFF body. Such movement may result in binding of the shaft and/or misalignment of the locking pin assembly, thereby making switching of the locking pin assembly less reliable. Further, such movement places substantial loading on the sides of the RFF body. The minimum width:of the RFF body is limited by the size of the high-lift roller/contact and the size of the lost-motion springs required to control the mass of the high-lift roller. Additionally, the low-lift rollers, which are mounted on the outside of the RFF body, may increase the width of the switching RFF assembly to a point where it is too wide to fit into many modern engine designs.
Therefore, what is needed in the art is a switching RFF having a reduced width.
Furthermore, what is needed in the art is a switching RFF that provides suitable high-lift contact with efficient packaging for the required lost motion springs.
Even further, what is needed in the art is a switching RFF that reduces the mass of the reciprocating high-lift roller/contact to allow a reduction in the size of the lost motion springs.
Even further, what is needed in the art is a switching RFF that provides a suitable bearing surface for the low-lift rollers and a compact. means to retain same.
Still further, what is needed in the art is an RFF that reduces the potential for locking pin assembly misalignment, thereby improving the reliability of mode switching in the RFF.
Moreover, what is needed in the art is an RFF that reduces the likelihood of the shaft binding within the grooves, thereby improving the reliability of mode switching in the RFF.
The present invention provides a deactivation and/or two-step roller finger follower for use with an internal combustion engine.
The invention comprises, in one form thereof, an elongate body having first and second opposing sides each having respective inside surfaces. First and second grooves are defined by the respective inside surfaces. A slider bracket includes a top plate having a top surface that is substantially perpendicular to the first and second sides. First and second projections are affixed to or integral with the top plate, and protrude therefrom in a generally parallel manner relative to the top surface. The first projection is slidably disposed within the first groove and the second projection is slidably disposed within the second groove. A locking pin assembly is carried by the slider bracket, and selectively couples and decouples the slider bracket to and from the body.
An advantage of the present invention is that the RFF has a reduced width.
Another advantage of the present invention is that the RFF provides a suitable high-lift contact with efficient packaging for the required lost motion springs.
A further advantage of the present invention is that the RFF has a suitable bearing surface for the low-lift rollers and a compact means to retain same.
A still further advantage of the present invention is a reduction of movement of the shaft in a direction generally transverse to the RFF body and/or grooves thereof, and thereby increases reliability in the operation of the locking pin assembly.
An even further advantage of the present invention is a reduced likelihood of locking pin misalignment, and thus increased reliability in mode switching of the RFF.